393 research outputs found
Returning to the Flint Hills
It was December of 1914. A short four months earlier the fighting in Europe had broken out in the great conflagration that would be known as “the war to end all wars.
Influence of dietary lysine on growth performance of high-lean growth gilts fed from 160 to 300 lb
One-hundred eight high-lean growth gilts (159.6 lb) were used to determine the
dietary lysine requirement to optimize
growth performance from 160 to 300 lb.
The experiment was designed as a randomized
complete block, with initial weight serving as the blocking factor. Six dietary treatments were used, ranging from .44 to
.94% digestible lysine (.59 to 1.16% total
lysine). Pigs were housed in pens of three,
with six replicate pens/treatment. Pig
weights and feed disappearance were collected
weekly to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (F/G). Average daily gain increased from 160 to 230 lb, from 230 to 300 lb, and from 160 to 300 lb. Average daily feed intake was not influenced by dietary treatment. The gilts consumed 6.47, 6.65, and 6.56 lb/day from 160 to 230, from 230 to 300, and from 160 to 300 lb, respectively. Thus, F/G improved linearly from 160 to 230 lb and quadratically from 230 to 300 and from 160 to 300 lb as a function of increased ADG. Lysine intake was increased linearly for all three weight periods as digestible lysine increased in the diet. The data from this experiment suggest that high-lean growth gilts requires at least 26 g/d of lysine from 160 to 230 and from 230 to 300 lb. Thus, matching nutrition with genetics is essential to optimize both rate and efficiency of gain
Constraints on decay plus oscillation solutions of the solar neutrino problem
We examine the constraints on non-radiative decay of neutrinos from the
observations of solar neutrino experiments. The standard oscillation hypothesis
among three neutrinos solves the solar and atmospheric neutrino problems. Decay
of a massive neutrino mixed with the electron neutrino results in the depletion
of the solar neutrino flux. We introduce neutrino decay in the oscillation
hypothesis and demand that decay does not spoil the successful explanation of
solar and atmospheric observations. We obtain a lower bound on the ratio of the
lifetime over the mass of , (\tau_2/m_2) > 22.7 (\srm/\MeV) for the
MSW solution of the solar neutrino problem and (\tau_2/m_2) > 27.8
(\srm/\MeV) for the VO solution (at 99% C.L.).Comment: 8 pages latex file with 4 figure
Electron energy loss and induced photon emission in photonic crystals
The interaction of a fast electron with a photonic crystal is investigated by
solving the Maxwell equations exactly for the external field provided by the
electron in the presence of the crystal. The energy loss is obtained from the
retarding force exerted on the electron by the induced electric field. The
features of the energy loss spectra are shown to be related to the photonic
band structure of the crystal. Two different regimes are discussed: for small
lattice constants relative to the wavelength of the associated electron
excitations , an effective medium theory can be used to describe the
material; however, for the photonic band structure plays an
important role. Special attention is paid to the frequency gap regions in the
latter case.Comment: 12 pages, 7 figure
Stringent Constraints on Cosmological Neutrino-Antineutrino Asymmetries from Synchronized Flavor Transformation
We assess a mechanism which can transform neutrino-antineutrino asymmetries
between flavors in the early universe, and confirm that such transformation is
unavoidable in the near bi-maximal framework emerging for the neutrino mixing
matrix. We show that the process is a standard Mikheyev-Smirnov-Wolfenstein
flavor transformation dictated by a synchronization of momentum states. We also
show that flavor ``equilibration'' is a special feature of maximal mixing, and
carefully examine new constraints placed on neutrino asymmetries. In
particular, the big bang nucleosynthesis limit on electron neutrino degeneracy
xi_e < 0.04 does not apply directly to all flavors, yet confirmation of the
large-mixing-angle solution to the solar neutrino problem will eliminate the
possibility of degenerate big bang nucleosynthesis.Comment: 11 pages, 6 figures; minor changes to match PRD versio
Nonlinear ion-acoustic (IA) waves driven in a cylindrically symmetric flow
By employing a self-similar, two-fluid MHD model in a cylindrical geometry,
we study the features of nonlinear ion-acoustic (IA) waves which propagate in
the direction of external magnetic field lines in space plasmas. Numerical
calculations not only expose the well-known three shapes of nonlinear
structures (sinusoidal, sawtooth, and spiky or bipolar) which are observed by
numerous satellites and simulated by models in a Cartesian geometry, but also
illustrate new results, such as, two reversely propagating nonlinear waves,
density dips and humps, diverging and converging electric shocks, etc. A case
study on Cluster satellite data is also introduced.Comment: accepted by AS
The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets
This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics
Study of Tau-pair Production in Photon-Photon Collisions at LEP and Limits on the Anomalous Electromagnetic Moments of the Tau Lepton
Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using
data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000.
The corresponding integrated luminosity is 650 pb^{-1}. The values of the
cross-section obtained are found to be in agreement with QED predictions.
Limits on the anomalous magnetic and electric dipole moments of the tau lepton
are deduced.Comment: 20 pages, 9 figures, Accepted by Eur. Phys. J.
CP asymmetry in in a general two-Higgs-doublet model with fourth-generation quarks
We discuss the time-dependent CP asymmetry of decay in an
extension of the Standard Model with both two Higgs doublets and additional
fourth-generation quarks. We show that although the Standard Model with
two-Higgs-doublet and the Standard model with fourth generation quarks alone
are not likely to largely change the effective from the decay of
, the model with both additional Higgs doublet and
fourth-generation quarks can easily account for the possible large negative
value of without conflicting with other experimental
constraints. In this model, additional large CP violating effects may arise
from the flavor changing Yukawa interactions between neutral Higgs bosons and
the heavy fourth generation down type quark, which can modify the QCD penguin
contributions. With the constraints obtained from processes
such as and , this model can lead to the
effective to be as large as in the CP asymmetry of .Comment: 13 pages, 5 figures, references added, to appear in Eur.Phys.J.
Energy dependence of Cronin momentum in saturation model for and collisions
We calculate dependence of Cronin momentum for and
collisions in saturation model. We show that this dependence is consistent with
expectation from formula which was obtained using simple dimentional
consideration. This can be used to test validity of saturation model (and
distinguish among its variants) and measure dependence of saturation
momentum from experimental data.Comment: LaTeX2e, 12 pages, 8 figure
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